Solar Powered Bird Feeder for Biological Research

In this post, I will discuss how we are working to revolutionize bird research by creating a solar powered bird feeder with a range of data collection capabilities. I will focus on how we have worked to decrease the power consumption of the raspberry Pi and increase the run time of the system in the field using solar power.

For years, ornithological research has been conducted with biologists sitting in a field, staring at a feeder. I’m an undergraduate researcher in the Ecophysiology Lab of Radford University, and we wanted to improve upon this approach. We founded the PASSER Project (Programmable Automated System for Songbird Ecobehavioral Research) to build a semi-autonomous, microcomputer-enabled bird feeder. This feeder is capable of 24/7 data collection of environmental (temperature, humidity, time of day, etc.) and behavioral metrics (photos, videos, response times, feeding times, etc.) relating to bird behavior. The feeder removes the time and labor intensive aspects of observation, making it possible to gather more data with less work.

The feeder gathers data during each feeding event and stores it on a swappable USB drive. With this data, my team and I hope to develop a better understanding of the daily feeding trends of local bird species as well as the long term feeding patterns across different species, habitats, and years.

Photo of a Tufted Titmouse (Baeolophus bicolor) taken by the feeder

One of the largest problems of developing these systems was power, as these feeders are often located far off the grid. While designing the feeder, we used a few different techniques to increase the longevity (and safety) of the battery. Here’s how we did it:

Side of the feeder showing the angle of the solar panel

Components

Voltaic 9 Watt Solar Panel: Using this 8.7 x 10.1 x 0.2 in. panel, we are able to cash in on the peak power performance when the panel is angled at 45 degrees in February (this angle is the optimum for our location in southwest Virginia, see other angles below). We custom designed 3D printed mounts for this panel to be fixed atop of our feeder. For this we used the screws on the bottom side of the panel creating slots in the mounts that they could slide into, allowing easy removal of the panel. The mounts can be found for download here: http://www.thingiverse.com/thing:2136348. This solar panel works great with the V44 battery back!

Voltaic V44 battery pack: We chose this battery because of its “always on” ability. This feature allows for the feeder to remain on, collecting data 24/7. The whole point of this project! This battery has two USB outputs: 5V/2A and 5V/1A. To power the Pi, we use the 5V/1A port. Also, we can stack these batteries by using the USB – 5.5×2.1mm Cable to connect one battery to another if double the power storage is necessary. We store the battery in another custom designed 3D printed box located bellow the solar cell. This location provides protection from the elements such as rain and direct sunlight. Electrical tape and hydrophobic spray are also used to ensure the battery is protected from water damage. The battery box, and battery box lid can be found for download here: http://www.thingiverse.com/thing:2136341.

Raspberry Pi 0: The Raspberry Pi 0 is the smallest microcomputer Raspberry Pi sells at 2.6″ x 1.2″ x 0.2″. The Pi 0 was selected for its low power consumption (80 mA – 120 mA), and $5 price point. The Pi 0 has 2 microUSB ports, one for power and one for a device of your choice. We use a USB to microUSB cord from the battery to the pi for power and a USB Hub in the device port to allow for multiple devices to be plugged in at once. We run Python on the Pi to collect the data and images being gathered by the attached sensors. If the Raspberry Pi 0 isn’t powerful enough for you, the Raspberry Pi 3/3+ can be used as an alternative, but be aware that the Pi 3/3+ draws more power (180 mA – 220 mA). The Pi 3/3+ also costs $36. Data can be stored on the SD card, or an external USB drive.

Solar Panel Angles

For our location at Radford University in southwest Virginia, we use these solar panel angles every month to receive the most sunlight possible:

Obviously, with a varying amount of direct sunlight, batteries will charge at different rates. Our feeders are typically placed in one of two general types of locations: urban or rural.

When placed in an urban habitat, buildings often shade the solar panel and reduce power production. The first location of our feeder was on Radford University’s campus between two 5 story buildings. On a sunny day, this was no problem as the solar panel received enough sunlight to fully recharge the battery. With repeated cloudy days, the battery wouldn’t always receive enough power to survive. This is a situation where increasing the battery size, or linking multiple batteries together would be helpful as a buffer to outlast the bad weather.

In more rural habitats, trees and general foliage can shade the panel. To bypass this, we would do one of two things: Place the feeder on a pole mount in a field (Opposed to hanging it from a tree) or use a cable extender from the panel to the battery on the feeder. The extender we use is the Voltaic 10 Foot Extension – 3.5×1.1mm. This cable allows for us to place a solar panel above the tree canopy to achieve more sunlight to charge the batteries throughout the night. This technique can also be used in woody backyards.

The Raspberry Pi 0 typically uses around .8 watts when idle with multiple USB plugins. This means that with 1 full charge of the Voltaic V44 battery (and no power to the solar panel), 55 hours of idle usage can be run. When being used by a bird, 1.5 watts can be used, but only for a short period of time. If power usage is still a problem, there are a few tricks that can be tried.

The other side of the feeder showing the port for the solar panel to charge the V44 battery

Ways to limit power use of the Pi 0

An average of 200mA (8 hours) of power can be conserved by:

Disconnect the LED Lights (̴5mA per LED)

Only saving about 5mA per LED, this technique is by far the least effective. However if you’re on the brink of having your battery die, this can be that extra power saver that keeps your unit running.

Limit daemons (̴100mA per daemons)

Keep the code simple and run one application at a time. Background applications use additional power. Most sensors/applications that you attach/install with your Pi will come with a power saver component that enhances the longevity of the battery.

Limit use of USB plugins (̴50mA per unit)

Each USB attachment draws power, so limit your use of these pieces of equipment and you will extend your battery life. For example, if you use a camera and a microphone in separate USB ports, this will draw more power than using a camera with a microphone installed in the same unit. We do not use this on our feeders, but if it came down to it, we would do this.

Disable HDMI (̴25 mA)

The HDMI port is helpful when developing code on the Pi itself and for debugging. However, once the Pi is deployed, disabling the HDMI port can save you crucial power.

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One Response

What did you use to charge the battery, or I should say how do you connect the solar panel to charge the battery? I’m building one of these to take video of the birds at the feeder. I have a RPI3 with a battery charger to run the camera and start recording to a USB drive when a bird lands on the feeder area. I’m building it into the bottom floor of a 2 story bird house. I am thinking about putting a camera inside the top floor but I need to work out all the power needs.